1. Field of the Invention
The present invention relates to an additive (blending agent) for resins, which is blended into olefin resins. More specifically, the invention relates to a blending agent for resins, that imparts excellent properties to the formed films such as anti-blocking property, stability, abrasion resistance and like properties. Particularly, the present invention relates to an olefin resin composition which contains an olefin resin and, particularly, an olefin resin obtained by using a metallocene catalyst and a particular inorganic blending agent, exhibiting excellent properties such as stability, abrasion resistance, antifoaming property and the like properties.
2. Prior Art
Olefin resins such as polyethylene, polypropylene and olefin copolymer have excellent moldability, sanitary properties, mechanical properties and transparency, and can be easily disposed of. Therefore, the olefin resins have been extensively used for a variety of applications in the form of films, such as packaging materials, agricultural films, etc.
In handling these films and, particularly, drawn films, there takes place a so-called blocking which causes the films to intimately adhere to each other making it difficult to peel them off. In order to prevent the blocking, an antiblocking agent has in many cases been blended. Examples of the antiblocking agent include various inorganic particles, such as amorphous silica, alumina, silica-alumina, zeolite and various clays.
Japanese Patent Publication No. 36866/1986 filed by the present applicant discloses an alumina-silica resin blending agent comprising cubic particles having a side of a length of not larger than 5 microns and a molar ratio Al.sub.2 O.sub.3 :SiO.sub.2 of from 1:1.8 to 1:5.
Furthermore, Japanese Patent Publication No. 42367/1993 discloses amorphous silica or silica alumina particles having circularity and ruggedness lying within predetermined ranges, the particles being obtained by synthesizing zeolite particles having an X-ray diffraction image specific to P-type zeolite, clearly spherical shape and rugged surfaces, and treating the zeolite particles with an acid.
Moreover, Japanese Patent Publication No. 17217/1994 discloses amorphous silica-alumina spherical particles obtained by ion-exchanging the P-type zeolite with an alkaline earth metal followed by calcining.
The above-mentioned silica or silica-alumina definite particles offer advantages in that they can be easily blended and dispersed into olefin resins and exhibit antiblocking property, but are not still satisfactory from the standpoint of hygroscopic property, abrasion resistance and stability in combination.
The cubic particles of the above-mentioned first proposal exhibit relatively large abrasion resistance when the films are rubbed by each other. The cubic particles, which is calcined in order to decrease the hygroscopic property, has a great like this.
The spherical particles of the above-mentioned second proposal still exhibit large hygroscopic property and tend to be deformed when they are being blended into the resin and are worked. At the time of production, furthermore, silica in the P-type zeolite elutes out into the reaction medium causing the yield of the object produce to decrease.
The spherical particles according to the third proposal are satisfactory in regard to a large yield of the object product and a relatively small hygroscopic tendency leaving, however, a problem in regard to stability when they are blended into the resin due to their strongly alkaline property. Therefore, the blending agent for resins is decomposed or is colored.
As described above, the blending agent for resins, such as antiblocking agent must assume definite particulate shape such as spherical shape to maintain dispersion property. At the same time, the blending agent must have a pH value which is nearly neutral, must impart stability to the resin composition, must suppress the abrasion resistance to a low level when blended into the resin films, must not exhibit large hygroscopic tendency, and must suppress foaming of the resin.